Removal of inorganic trace contaminants by electrodialysis in a remote Australian community

Water provision for developing countries is a critical issue as a large number of lives are lost annually due to lack of access to safe drinking water. The presence and fate of inorganic trace contaminants is of particular concern. Trace inorganic contaminants have been found in elevated concentrations in drinking waters supplied directly from brackish groundwaters in developing countries. Desalination and the removal of trace inorganic contaminants from bore water sources from a remote community in Australia using electrodialysis (ED) were investigated. The influence of applied voltage on the removal of the trace contaminants was evaluated. While the results from this study demonstrated that ED is an effectual method for the removal of total dissolved solids and a number of trace inorganic contaminants from brackish groundwaters to below drinking water guideline levels, the deposition of trace contaminants on the membranes (fouling) influenced the ED process in relation to ionic flux and the effectiveness of trace contaminant removal.

The results from this study demonstrated the performance of an ED system in the treatment of groundwater of high salinity and trace contaminant concentration from an isolated community in Central Australia. The removal of TDS was successful in that the treated bore water was below drinking water quality guideline levels. The applied voltage had an influence on the removal of the trace contaminants from the bore water, with 12 V overall being the most effective. Results also demonstrated that ED was effective in reducing the concentration of the contaminants chloride, fluoride, sodium and sulphate to below guideline levels. However, fouling of the ion-exchange membranes is a critical issue. The deposition of trace contaminants on the ion-exchange membranes had an influence on the overall stack resistance throughout the experiments with a significant increase occurring in the later stages of the ED process. This increase in stack resistance was due to the formation of a fouling (scaling) layer on or in the membranes. This fouling layer in turn influenced the flux of TDS and trace contaminants from the diluate into the concentrate. This has an influence on the practical applicability of ED in the treatment of waters from remote communities in developing regions and further work is required to control such fouling.